Added missing periods to ends of sentences. (#1535)

This change is done to keep things more consistent and have all
sentences end with periods. Previously, most sentences had periods
at the end, but not all.

This makes the document a little more professional looking and
raises the Awesome quality standard higher.

.github/PULL_REQUEST_TEMPLATE.md

@@ -12,11 +12,12 @@ Very good coverage
 **Note**: that new categories can be added only when there are 3 packages or more.
 
 **Make sure that you've checked the boxes below before you submit PR:**
-- [ ] I have added my package in alphabetical order
-- [ ] I know that this package was not listed before
-- [ ] I have added godoc link to the repo and to my pull request
-- [ ] I have added coverage service link to the repo and to my pull request
-- [ ] I have added goreportcard link to the repo and to my pull request
+- [ ] I have added my package in alphabetical order.
+- [ ] I have an appropriate description with correct grammar.
+- [ ] I know that this package was not listed before.
+- [ ] I have added godoc link to the repo and to my pull request.
+- [ ] I have added coverage service link to the repo and to my pull request.
+- [ ] I have added goreportcard link to the repo and to my pull request.
 - [ ] I have read [Contribution guidelines](https://github.com/avelino/awesome-go/blob/master/CONTRIBUTING.md#contribution-guidelines), [maintainers note](https://github.com/avelino/awesome-go/blob/master/CONTRIBUTING.md#maintainers) and [Quality standard](https://github.com/avelino/awesome-go/blob/master/CONTRIBUTING.md#quality-standard).
 
 Thanks for your PR, you're awesome! :+1:

CONTRIBUTING.md

@@ -13,7 +13,7 @@ To set this list apart from and complement the excellent [Go wiki Projects page]
 - Each item should be limited to one link.
 - The link should be the name of the package or project.
 - Descriptions should be clear, concise, and non-promotional.
-- Descriptions should follow the link, on the same line.
+- Descriptions should follow the link, on the same line and end with a punctuation mark.
 - At least 3 items are needed to create a new category.
 
 Please contribute links to packages/projects you have used or are familiar with. This will help ensure high-quality entries.